Sent to the IDBDatabase object representing a database connection when the database is unexpectedly closed. This happens after all transactions have been aborted. You can use IDBDatabase.onclose to establish the event handler.

Some browsers used a close event to indicate that a given Worker had shut down; this was at one point part of the specification, but has been removed from the spec, and browsers are in the process of removing support for this event in the Web Workers API.